Maciej Rozycki <maciej.rozy...@imgtec.com> writes:
> Fix `-mrelax-pic-calls' support for microMIPS code where the relocation
> produced is supposed to be R_MICROMIPS_JALR rather than R_MIPS_JALR.
> The lack of short delay support comes from a missed update to this code
> for microMIPS support and can be relieved as JALRS and JRS instructions
> can be relaxed to BALS and B instructions respectively, so do that as
> well.
Thanks. I didn't follow the background to this optimisation when I added
the compact branch support so opted to retain the pre-existing behaviour.
> By doing so complement commit r196828 ("microMIPS gcc support"),
> <https://gcc.gnu.org/ml/gcc-patches/2013-02/msg01103.html>, which is the
> original change that introduced microMIPS support, in particular to
> MIPS_CALL, which is where this code previously resided.
>
> Adjust the test suite accordingly, limiting R_MICROMIPS_JALR cases to
Typo fwiw: Should say R_MIPS_JALR for MIPS code.
> regular MIPS code only, and adding corresponding R_MICROMIPS_JALR cases
> for microMIPS code.
>
> gcc/
> * config/mips/mips.c (mips_output_jump): Output R_MICROMIPS_JALR
> rather than R_MIPS_JALR relocation in microMIPS code. Do not
> cancel short delay slots in PIC call relaxation.
>
> gcc/testsuite/
> * gcc.target/mips/call-1.c (dg-options): Add `-mno-micromips'.
> (dg-final): Remove microMIPS JALRS mnemonic matching.
> * gcc.target/mips/call-2.c (dg-options): Add `-mno-micromips'.
> (dg-final): Remove microMIPS JALRS mnemonic matching.
> * gcc.target/mips/call-3.c (dg-options): Add `-mno-micromips'.
> (dg-final): Remove microMIPS JALRS mnemonic matching.
> * gcc.target/mips/call-4.c (dg-options): Add `-mno-micromips'.
> * gcc.target/mips/call-5.c (dg-options): Add `-mno-micromips'.
> * gcc.target/mips/call-6.c (dg-options): Add `-mno-micromips'.
> * gcc.target/mips/call-1u.c: New test case.
> * gcc.target/mips/call-2u.c: New test case.
> * gcc.target/mips/call-3u.c: New test case.
> * gcc.target/mips/call-4u.c: New test case.
> * gcc.target/mips/call-5u.c: New test case.
> * gcc.target/mips/call-6u.c: New test case.
> ---
> NB the use of this feature for microMIPS is limited because short
> encodings of register jump instructions usually do not have their branch
> counterparts and long encodings typically are not used. However at
> least
> tail calls can be converted if the jump target is in range, as can calls
> in `-minsn32' code. Perhaps we could switch to producing `j[al]r[s].32'
> in the `-mrelax-pic-calls' mode like GAS does with the `jal' and `j'
> microMIPS macros in PIC code.
Does the linker do anything for R_MICROMIPS_JALR currently? From memory
I seem to think it was mostly ignored. Is there any risk with older linkers
by introducing R_MICROMIPS_JALR in GCC generated code?
> Let me know if the lack of microMIPS results would be a problem for
> this
> patch's acceptance.
Not a problem. We will pick this up as part of testing for the release.
There is a bit of coding style fuzz in the testcases but it is
pre-existing from the code you duplicated so I don't think it needs
fixing.
> Otherwise, OK to apply?
OK, as long as you can say there is no risk with the new reloc and older
linkers.
Thanks,
Matthew
